Film printing machine



y 13, 1952 J. H. cooTE ET AL FILM PRINTING. MACHINE 3 Sheets-Sheet 1Filed Aug. 9, 1948 llnrncy y 13, 1952 J. H. COOTE ET AL 2,596,373

FILM PRINTING MACHINE Filed Aug. 9, 1948 .3 Sheets-Sheet 2 wnvenlou,

Attorney May 13, 1952 J. H. COOTE ET AL FILM PRINTING MACHINE 3Sheets-Sheet 3 Filed Aug. 9, 1948 MW Nm /4 55 4 fliy zh Patented May 13,1 952 FILM PRINTING MACHINE Jack Howard Coote and Arthur Philip Jenkins,London, England, assignors to Dufay-Chromex Limited, London, England, aBritish company Application August 9, 1948, Serial No. 43,258 In GreatBritain May 14, 1947 6 Claims. 1

This invention relates to a film-printing machine which is capable ofuse in making contact prints through the thickness of the film base.

Two general types of film-printing machine are available. In one thelight output is maintained substantially constant and the amount oflight reaching the exposure plane is controlled by means of a variableiris type of aperture and diffusers are inserted between the iris andthe exposure plane so as to secure a substantially even illumination atthe latter. When this system is used to print colour records the slightbut noticeable differences in evenness in the records printed atdiffering light apertures may result in uneven colouring of the print.Moreover, on account of the use of the diffusers it is not possible toobtain satisfactory prints by printing through the thickness of the filmbase.

In the second general type in order to dispense with apertures anddiffusers provision is made for varying the intensity of the light byproviding resistances which may be brought into and taken out of circuitin predetermined manner. However, in printing images whose densitieshave to be accurately controlled, as, for example, in colourcinematography, it is found not to be readily feasible to control thelight output within the desired limits owing to such factors as thetemperature coefficient of the resistances and possible change inapplied voltage with change in load due to the changing of theresistance in circuit.

The present invention seeks to overcome these difficulties by providinga printer in which the light output of the printer is maintainedsubstantially constant during printing operations and the time ofexposure is varied in a predetermined manner. Accurate control of theprinting operation has been found possible in this way and printingthrough the film base can be readily carried on.

According to the present invention a filmprinting machine comprisesmeans for varying in predetermined manner the time interval during whicha substantially parallel beam of light of substantially constantintensity is incident upon a film-exposure plane.

The apparatus in accordance with the present invention may comprise anoptical system for producing a substantially parallel beam of light, afirst rotatable cut-off shutter adapted to interrupt said beam of light,means for driving the rotatable shutter, a second rotatable cut-offshutter adapted to interrupt said beam of light, means for driving thesecond rotatable cut-off shutter, film-confining means including anexposure aperture in the path of said beam of light, film transportmeans associated with the film-confining means and manually operablemeans for varying the phase relationship between the two rotatablecut-off shutters so as to vary in predetermined manner the time intervalduring which light passes both shutters and is incident upon aphotographic negative being printed during its passage through thefilm-confining means.

According to a feature of the invention the film-transport means isdriven by the same power source as the first rotatable cut-off shutter.

In one form of apparatus in accordance with the invention provision ismade for mounting a substantially point source of light and this ismounted in spaced relation to a lens system so that the light passingtherethrough from the point source is rendered substantially parallel.The path of the resulting beam of light is intercepted by two separatelyrotatable shutters. These shutters may be of the type normally used oncinematograph cameras. They are so mounted that during rotation of eachone the apertured portion passes through the path of the beam of light.The shutters are mounted for rotation independently of each other andmay, for example, be driven by a pair of electric motors which areelectrically interlocked so that one motor is the master motor while theother is the follower motor and they rotate in synchronism. The twocut-off shutters are so set with respect to each other that during apart of one complete revolution light passes both. By varying the phaserelationship between the two shutters the angle over which light passesboth, and thus the time interval during which light passes may bevaried. Accordingly provision is made for varying the phase of thefollower motor by providing for rotation of the stator of that motor toany desired extent at any predetermined time when the machine is in use.

The invention will now be described with reference to the accompanyingdrawings in which:

Figure l is a front elevation of a film printer constructed inaccordance with the invention showing the paths which the positive andnegative films follow.

Figure 2 is a sectional view along the line AA of Figure l and Figure 3is a detailed view of one form of manual means for varying the phaserelationship of the rotatable cut-off shutters.

Referring to Figure 1 of the drawings positive stock for printing isdrawn from the reel I to the film printing plane 3 by the sprocket Z andis then drawn away by the sprocket 4 and taken up upon reel 5. Similarlynegative film to be printed is drawn from reel 6 by sprocket I to thefilm printing plane 3 and is then drawn away by the sprocket 8 to thenegative take up reel 9. Film transport means for moving both negativeand positive films past the exposure aperture is housed under the casingl and may be of conventional type. Guide rollers H, [2, l3 and M areprovided along the path of the positive being printed and similarrollers l5, l5, l1 and [8 are also provided along the path of thenegative.

Referring more particularly to Figure 2 the lamp 2!! provides asubstantially constant source of illumination. There may be included incircult with the lamp one or more variable resistances by variation ofwhich compensation may be applied for the tendency of the light outputof the lamp to diminish with age or through other causes: this is notshown upon the drawings. A collimating lens system, shown at 2| isprovided for producing a parallel beam of light, the lamp 28 being soinclined with respect thereto that the line filament appearssubstantially as a point source. Light from lamp 29 after passingcollimating lens system 2i'is incident upon a front surface reflectingmirror 22 which is inclined at an angle of 45 with respect to the axisof the beam of light.

Before reaching the surface of mirror 22 the light has to pass the planeof. a rotatable shutter 23 driven from the followermotor 24, the statorof which motor is attached to and rotatable with a gear wheel 25 theposition of which is manually controlled by means hereinafter to bedescribed. After reflection at mirror 22 the light reaches the plane ofthe second rotatable shutter 26. The shutter 26 is mounted upon theshaft 21 of the master motor 28. Also mounted upon shaft 21 are cams 29which operate the film transport mechanism housed within the housing I0.Shutter 26 being connected to the master motor 28 rotates at constantspeed. Shutter 23 being mounted upon the shaft of follower motor 24 canhave its phase varied with respect to that of shutter 26 and in this waythe interval during which light passes both shutters can be varied.

One method of controlling the phase relationship of the two shutters isshown in Figure 3.

A pointer arm 39, manually operable by a handle 35A, is provided mountedupon a pivot. On the front of the printer a scale 32 (Figure l) isprovided having a number of setting positions indicated thereon. Thepivot is adapted to co operate with an arm 33 so as to impart alongitudinal to and fro movement thereto through the intervention of arack and pinion device 31, 3 IA. The arm 33 which is supported. in guideblocks 50 and contains a link 34 pivoted at 34A, is provided with aroller 35 at one end thereof as well as an articulately mounted rod 36which carries a spring 3'! always held in compressionv thereon. lheupper end of rod 36 is carried in the bracket 38 which is'mounted uponbase 39 which is itself pivotally supported at 40.

The roller 35 is normally urged into the bottom of a V-groove 42 formedas a part of a swinging arm 4!. Arm 4| is secured to base 39 as byrivets 43 and at its other end 44 is pivoted to a link 45, which ispivoted to arm 46 at 41. The arm 45 which is mounted in guide blocks59,'is provided with an electromagnetic release generally designated 48.Arm 45 also carries a rack 49 which meshes with the gear wheel 25 whichrotates the stator of follower motor 24.

The electromagnetic release -48 is operated-by means of an indicationprovided upon the negative being printed. This may take the form of anotch in the side of the film. A roller is urged into contact with theside of the film and upon entering a notch closes the contacts 50 of anelectrical circuit. In parallel with the contacts 50 are a resistance 5!and capacitance 52 so as to minimize sparking across the contacts. Inseries are a switch 53, a source of E. M. F. 54 and a solenoid mountedwithin the housing 55. The plunger 56 is mounted within a guide 51 whichis surrounded by the solenoid. Plunger 56 is normally urged upwards bythe spring 51 into frictional engagement with the arm 45. The frictionalengagement is sufiicient to hold the arm against longitudinal movementwhen the roller 35 is part way up either of the inclined planes of theV-groove 42. Such frictional engagement is only interrupted when thecircuit is momentarily completed through the contacts and the solenoidin housing 55 is actuated. During such interruption the downward thrustof spring 31 urges the roller 35 to the bottom of the V-groove 42 and inso doing drives the gear Wheel 25 into a new position in which it ismaintained by the frictional engagement between plunger 51 and arm 46until the circuit is again broken.

Instead of having a notch in the side of the film a metal insert may beprovided which momentarily completes the circuit and actuates thesolenoid.

The exposure intervals are determined in advance of printing andtranslated into the corresponding indications upon scale 32. A length ofleader film should be provided so that the motors have reached theconstant printing speed before the negative to be printed commences torun through the apparatus which has been set at the first printingindication so that the follower motor then adjusts itself in accordancewith that indication when the frame opposite which the notch is cut inthe negative is moved forward to the exposure position and in so doingcloses the contacts 50 and drives the gear wheel 25 to the correspondingposition. As soon as the follower motor has been driven to the desiredposition the next manual presetting of arm 30 maybe made and operationthen continues until printing is completed or is interrupted for anyreason.

The cut-off shutters need not be driven by electric motors as justdescribed although these are very convenient and therefore preferredforthis purpose. Other means may also be used for transmitting thepresetting to the variable shutter. Thus the transmission member mayoperate gearing or a worm and collar device may be employed.

The shafts carrying the cut-off shutters may be mounted concentricallyif desired but they are preferably separately mounted and each connectedto the shaft of an electric motor as already indicated.

Since a substantially parallel beam of light is employed the apparatusin accordance with the present invention may be used for contactprinting through the base of the film. The apparatus may therefore beused for printing the innermost layer of a multilayer material throughthe emulsion support. Moreover, since diffusers .are not employed a highintensity illumination at the exposure plane can be secured without theuse of a lamp of abnormally high wattage as the light source. Inaddition fine grain materials may be satisfactorily printed using theimproved apparatus.

We claim:

1. A continuous step-contact printing machine comprising a casing, amount for a source of light within said casing, an optical system forproducing a parallel beam of light mounted in an aperture in saidcasing, a film exposure aperture in the path of said parallel beam oflight, a first rotatable cut-oif shutter so disposed as to interrupt thepath of light from said source to said exposure aperture during a partof each rotation thereof, an electric motor for continuously drivingsaid first shutter, a second rotatable cut-off shutter so disposed as tointerrupt the path of light from said source to said exposure apertureduring a part of each rotation thereof, an electric motor forcontinuously driving the second rotatable cut-off shutter in synchronismwith the first shutter, a single film transport mechanism forintermittently and simultaneously feeding successive frames of both atransparent photographic negative and unexposed photographic film incontact through said film exposure aperture while said beam of light isinterrupted by at least one of said shutters and means responsive to anindication provided upon said negative film for varying in apredetermined manner the phase relationship of said second motor withrespect to said first motor and thereby to vary between the printing ofsuccessive frames of said negative the time interval during which lightpasses both shutters and is incident upon successive frames of saidnegative.

2. A continuous step-contact film printing machine according to claim 1in which the means responsive to an indication provided upon saidnegative film for varying in predetermined manner the phase relationshipof the two motors is restrained from change by frictional engagementwith a member whose engagement therewith is interrupted by theactivation of a solenoid.

3. A machine according to claim 2 in which activation of the solenoid isefiected by the closure of an electric circuit by means of an indicatorcarried by the film being printed.

4. A continuous step-contact printing machine comprising a casing, amount for a source of light within said casing, an aperture in saidcasing, an optical system mounted upon said casing for collimating abeam of light passing through said aperture, film confining meanscomprising an exposure aperture in the path of said collimated beam oflight, a first rotatable cut-off shutter so disposed as to interrupt thepath of light from said source to said exposure aperture during a partof each rotation thereof, an electric motor for continuously drivingsaid first shutter, a second independently mounted rotatable cut-oilshutter so disposed as to interrupt the path of light from said sourceto said exposure aperture during a part of each rotation thereof, anelectric motor for continuously driving said second shutter insynchronism with the first shutter, film transport means forintermittently and simultaneously feeding successive frames oftransparent negative stock and positive stock in contact through saidfilm confining means while said beam of light is interrupted by at leastone of said shutters and means responsive to an indication provided uponsaid negative stock for varying in predetermined manner the phaserelationship of said'second motor with respect to said first motor andthereby to vary between the printing of successive frames of saidnegative stock the time interval during which light passes both huttersand is incident upon successive frames of said negative stock.

5. A continuous step-contact film printing machine according to claim 4in which the means responsive to an indication provided upon saidnegative film for varying in predetermined manner the phase relationshipof the two motors is restrained from change by frictional engagementwith a member whose engagement therewith is interrupted by theactivation of a solenoid.

6. A machine according to claim 5 in which activation of the solenoid iseffected by the closure of an electric circuit by means of an indicatorcarried by the film being printed.

JACK HOWARD COOTE. ARTHUR PHILIP JENKINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

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